Re: [PATCH] usb: typec: tcpm: always rediscover when swapping DR

[Guenter Roeck]

On 8/17/21 2:36 AM, Heikki Krogerus wrote:
> On Fri, Aug 13, 2021 at 12:31:31PM +0800, Icenowy Zheng wrote:
> > Currently, TCPM code omits discover when swapping to gadget, and assume
> > that no altmodes are available when swapping from gadget. However, we do
> > send discover when we get attached as gadget -- this leads to modes to be
> > discovered twice when attached as gadget and then swap to host.
> >
> > Always re-send discover when swapping DR, regardless of what change is
> > being made; and because of this, the assumption that no altmodes are
> > registered with gadget role is broken, and altmodes de-registeration is
> > always needed now.
> >
> > Signed-off-by: Icenowy Zheng <icenowy@xxxxxxx>
> > ---
> >   drivers/usb/typec/tcpm/tcpm.c | 9 ++++-----
> >   1 file changed, 4 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> > index b9bb63d749ec..ab6d0d51ee1c 100644
> > --- a/drivers/usb/typec/tcpm/tcpm.c
> > +++ b/drivers/usb/typec/tcpm/tcpm.c
> > @@ -4495,15 +4495,14 @@ static void run_state_machine(struct tcpm_port *port)
> >   		tcpm_set_state(port, ready_state(port), 0);
> >   		break;
> >   	case DR_SWAP_CHANGE_DR:
> > -		if (port->data_role == TYPEC_HOST) {
> > -			tcpm_unregister_altmodes(port);
> > +		tcpm_unregister_altmodes(port);
> > +		if (port->data_role == TYPEC_HOST)
> >   			tcpm_set_roles(port, true, port->pwr_role,
> >   				       TYPEC_DEVICE);
> > -		} else {
> > +		else
> >   			tcpm_set_roles(port, true, port->pwr_role,
> >   				       TYPEC_HOST);
> > -			port->send_discover = true;
> > -		}
> > +		port->send_discover = true;
> >   		tcpm_ams_finish(port);
> >   		tcpm_set_state(port, ready_state(port), 0);
> >   		break;
>
> Why is it necessary to do discovery with data role swap in general?
>
> thanks,

Additional question: There are two patches pending related to DR_SWAP
and discovery. Are they both needed, or do they both solve the same
problem ?

Thanks,
Guenter